Odd, you ask “how can there be any key factor”, and then you declare that “the innate bond between a child and their biological parents” is a key factor.

I did not say that the innate bond between a child and their biological parents” is a key factor. I said that there is no such thing as a key factor. There are just many factors, and determining the best situation there is no simplistic formula.

So you don’t believe in “key” factors? IOW, you don’t believe that there are factors that are critical, in order for a child to develop optimally?

If a child never develops a bond with a primary caregiver, that child WILL be socially, emotionally, and behaviorally messed up.

If a child suffers prolonged abuse or neglect, odds are that the child will be socially, emotionally, and behaviorally messed up.

If a child does not have proper mental and physical stimulation, that child will not reach their developmental potential.

Those are the primary responsibilities of someone who seeks to be an “ideal” parent. Just because I can state it simply, does not mean that it is simple to do or that there is any simple possible combination of secondary factors for accomplishing those. But if the relevant primary factors are accomplished, then the parenting, IMO, can be said to have been ideal, regardless of what the secondary factors that were involved in accomplishing the primary factors.

I agree., Ideal parenting is a relative term when it concerns child rearing. In some societies one tenet of ideal parenting consists of “spare the rod, spoil the child”, but is that truly ideal?